The invention relates to a method for the operation of an IC engine to achieve a low pollutant emission rate, in which the engine exhaust gases are led off through an thermal converter and to an arrangement for performing the method.
For the reduction of pollutant emission from automobile engines catalytic converters and more especially three-way catalytic converter have come into use as effective devices but which are somewhat high in price, largely because of the need to exactly regulate the ratio between the quantities of fuel and air.
Converters designed to cause catalytic oxidation are lower in price. They only reduce the emission of CO, unburned hydrocarbons and soot or particles.
In order to reduce the emission of pollutants from IC engines thermal converters have also been used, which perform their task without the use of catalytic materials owing to the maintenance of sufficiently high temperatures to oxidize CO, hydrocarbons and soot or particles in the exhaust gas.
Furthermore converters have been equipped with fuel burners in order to reach the conversion temperature during phases of engine operation which would otherwise not produce the necessary heating effect, but this also involves high costs.
The expense of such known equipment and fittings for reducing the emission of pollutants makes itself more especially felt when the purchase price of an automobile is low, that is to say particularly in the case of small, low horsepower cars.
During the course of design development IC engines with specially low pollutant emission rates have been evolved, which are able to be run near the statutory emission rates, but which in order to keep to such limits require a catalytic converter which leads to a high undesired increase in the purchase price of such a vehicle.